Surface state tunneling signatures in two-component superconductor UPt$_3$

TL;DR

This paper extends quasiparticle interference imaging to three-dimensional UPt$_3$ superconductor, analyzing how different gap models produce distinct surface states and signatures in QPI, potentially revealing the true gap structure.

Contribution

It introduces a 3D QPI analysis for UPt$_3$, identifying unique surface state signatures for different gap models to determine the superconductor's nodal structure.

Findings

Distinct QPI signatures for different gap models

Identification of Weyl arcs in surface states

Potential to determine UPt$_3$'s true gap symmetry

Abstract

Quasiparticle interference (QPI) imaging of Bogoliubov excitations in quasi-two dimensional unconventional superconductors has become a powerful technique for measuring the superconducting gap and its symmetry. Here, we present the extension of this method to three-dimensional superconductors and analyze the expected QPI spectrum for the two-component heavy fermion superconductor UPt$_3$ whose gap structure is still controversial. Starting from a 3D electronic structure and the three proposed chiral gap models $E_{1g,u}$ or $E_{2u}$, we perform a slab calculation that determines the 2D continuum Bogoliubov- de Gennes (BdG) surface quasiparticle bands and in addition the in-gap flat-band Andreev bound states that lead to surface Weyl arcs connecting the projected gap nodes. Both features are very distinct for the three models, in particular the most prominent $E_{2u}$ candidate is singled out by the existence of {\it two} Weyl arcs due to the double monopole node points. The signature of these distinct surface bound and continuum states that is left in QPI is derived and discussed. We show that it provides a fingerprint that may finally determine the true nodal structure of UPt$_3$ superconductor.